For the sake of science, Olav Oftedal has milked bats, bears and a lot of other mammals. But a naked mole-rat was something new.

“The thin, hairless skin is so translucent that you can see the milk accumulating in the mammary glands,” says Oftedal, of the Smithsonian Environmental Research Center in Edgewater, Md. For once he could tell exactly which glands were full.

“In most small mammals,” he says, “the big problem is you have hair that can wick the milk away. You have a capillary tube, and you’re trying to catch the milk so it can’t touch any hair.” Naked mole-rats, though, are helpfully hairless.

Oftedal collected milk from the queens of Heterocephalus glaber colonies at the Smithsonian’s National Zoo. In colonies of dozens or hundreds of mole-rats, only the queen reproduces.

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